linux-kernel - Re: [PATCH v4 2/2] iio: pressure: dps310: Reset chip if MEAS

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Message-ID: <CAHp75VdbRiWxxbnW61SNdj+pC4skeRF3prXgPvKB+btjW3dLKw@mail.gmail.com>
Date:   Sat, 13 Aug 2022 01:13:00 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     linux-iio <linux-iio@...r.kernel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Joel Stanley <joel@....id.au>
Subject: Re: [PATCH v4 2/2] iio: pressure: dps310: Reset chip if MEAS_CFG is corrupt

On Wed, Aug 10, 2022 at 12:12 AM Eddie James <eajames@...ux.ibm.com> wrote:
>
> Corruption of the MEAS_CFG register has been observed soon after
> system boot. In order to recover this scenario, check MEAS_CFG if
> measurement isn't ready, and if it's incorrect, reset the DPS310
> and execute the startup procedure.

Looks like both patches miss the Fixes tag. Can you add them?

...

> +/*
> + * Called with lock held. Returns a negative value on error, a positive value
> + * when the device is not ready, and zero when the device is ready.
> + */
> +static int dps310_check_reset_meas_cfg(struct dps310_data *data, int ready_bit)
> +{
> +       int meas_cfg;

> +       int rc = regmap_read(data->regmap, DPS310_MEAS_CFG, &meas_cfg);
> +
> +       if (rc < 0)
> +               return rc;

Please, split definition and assignment.

> +       /* Device is ready, proceed to measurement */
> +       if (meas_cfg & ready_bit)
> +               return 0;
> +
> +       /* Device is OK, just not ready */
> +       if (meas_cfg & (DPS310_PRS_EN | DPS310_TEMP_EN | DPS310_BACKGROUND))
> +               return 1;
> +
> +       /* DPS310 register state corrupt, better start from scratch */
> +       rc = regmap_write(data->regmap, DPS310_RESET, DPS310_RESET_MAGIC);
> +       if (rc < 0)
> +               return rc;
> +
> +       /* Wait for device chip access: 2.5ms in specification */
> +       usleep_range(2500, 12000);
> +
> +       /* Reinitialize the chip */
> +       rc = dps310_startup(data);
> +       if (rc)
> +               return rc;
> +
> +       dev_info(&data->client->dev,
> +                "recovered from corrupted MEAS_CFG=%02x\n", meas_cfg);
> +       return 1;
> +}
> +
>  static int dps310_read_pres_raw(struct dps310_data *data)
>  {
>         int rc;
> @@ -405,16 +443,26 @@ static int dps310_read_pres_raw(struct dps310_data *data)
>         if (mutex_lock_interruptible(&data->lock))
>                 return -EINTR;
>
> -       rate = dps310_get_pres_samp_freq(data);
> -       timeout = DPS310_POLL_TIMEOUT_US(rate);
> -
> -       /* Poll for sensor readiness; base the timeout upon the sample rate. */
> -       rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG, ready,
> -                                     ready & DPS310_PRS_RDY,
> -                                     DPS310_POLL_SLEEP_US(timeout), timeout);
> -       if (rc)
> +       rc = dps310_check_reset_meas_cfg(data, DPS310_PRS_RDY);
> +       if (rc < 0)
>                 goto done;
>
> +       if (rc > 0) {
> +               rate = dps310_get_pres_samp_freq(data);
> +               timeout = DPS310_POLL_TIMEOUT_US(rate);
> +
> +               /*
> +                * Poll for sensor readiness; base the timeout upon the sample
> +                * rate.
> +                */
> +               rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG,
> +                                             ready, ready & DPS310_PRS_RDY,
> +                                             DPS310_POLL_SLEEP_US(timeout),
> +                                             timeout);
> +               if (rc)
> +                       goto done;
> +       }

If you split the condition body to a helper, it can be rewritten like
(also note special definition for positive returned numbers):

  rc = ..._reset_meas_cfg(...);
  if (rc  == DPS310_MEAS_NOT_READY)
    rc = ..._new_helper_func(...);
  if (rc)
    goto done;

and looking at this it might be worth considering calling that
conditional in the middle in the _reset_meas_cfg(), so the latter will
return either 0 or negative error code.

> +       rc = dps310_check_reset_meas_cfg(data, DPS310_TMP_RDY);
>         if (rc < 0)
>                 goto done;
>
> +       if (rc > 0) {
> +               rate = dps310_get_temp_samp_freq(data);

Okay, I see this function is different, but still you may realize a
helper from below and something like above suggestion can still be
achieved.

> +               timeout = DPS310_POLL_TIMEOUT_US(rate);
> +
> +               /*
> +                * Poll for sensor readiness; base the timeout upon the sample
> +                * rate.
> +                */
> +               rc = regmap_read_poll_timeout(data->regmap, DPS310_MEAS_CFG,
> +                                             ready, ready & DPS310_TMP_RDY,
> +                                             DPS310_POLL_SLEEP_US(timeout),
> +                                             timeout);
> +               if (rc < 0)

Why out of a sudden ' < 0'?

> +                       goto done;
> +       }

As per above.

>         rc = dps310_read_temp_ready(data);


-- 
With Best Regards,
Andy Shevchenko